Etanercept (Enbrel): A warning goes out
Wyeth-Ayerst Laboratories and Immunex Corp. recently sent a joint letter to health care practitioners warning of adverse events seen in patients using etanercept (Enbrel), a drug approved in November 1998 for reducing symptoms and delaying structural damage in patients with moderately to severely active rheumatoid arthritis.
Although the manufacturer states that the causal effect of etanercept with the adverse events observed has not been determined, still, post-marketing reports involve patients taking etanercept. The adverse events reported include rare cases of central nervous system demyelinating disorders such as multiple sclerosis, myelitis, and optic neuritis. The manufacturer asks that etanercept be prescribed with caution in patients with a history of demyelinating disorders.
Further, the manufacturer reports rare cases of pancytopenia, including aplastic anemia. Some cases have had fatal outcomes. While the causal relationship is not fully established for this adverse event either, pancytopenia has been seen in some patients within two weeks of initiating etanercept therapy. The majority, but not all, of patients experiencing pancytopenia were taking other anti-rheumatic medications associated with myelosuppression either concomitantly with etanercept or in the recent history. Patients should be counseled to watch for signs and symptoms of blood dyscrasias or infection (e.g., persistent fever, bruising, bleeding) and to report any of these symptoms to their physicians immediately.
The labeling on etanercept has been changed as a result of these post-marketing events. The warning section now includes this information under neurologic and hematologic events. (For more information, see warning letter from Immunex at www.fda.gov/medwatch/safety/2000/enbrel1.pdf.)
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